Weird RAM issue encountered

[schen]

I've been trying to gather and rehab some older machine for my wife to use in her 3rd grade classroom. They've been mostly A31s so far, and those have been pretty straight forward, but limited. In light of that, I've picked up some donated T60 parts machines through the generosity of another forum member.

Oddly, although I have a fair amount of experience with T61s and Z61s; I've had very littel with the T60s. I know they are very similar to the Z61s, but there seems to be a fair amount of differences as well. I ran across and oddity that I've never seen before. On the T60 that I'm currently working on, I put a 2Gb RAM module in there along with a 1Gb module. The W7 load gave a memory error, so I took those out and put 2 different (both 1Gb) "known good" modules in from a Z61m. W7 then loaded fine after that. When it finished the load, I tried putting the 2Gb module back in and it worked this time. However, I realized I put it in a different socket than I did the first time, so I switched and sure enough, I got a memory error again.

So, what I have is that the machine is OK with a 2Gb RAM module in the top socket but not the bottom! This really isn't an issue, since these machines have a 3Gb BIOS limitation anyway, but I'm just curious about it. My Z61s don't seem to have this characteristic. Anyone have thoughts on this?

[emeraldgirl08]

I have experienced the finicky RAM on a T400 and an R51e. Unfortunately I do not have an inkling on why I encountered such behavior as well. It was annoying when I bought and had to return two known good sticks of RAM to a trusted source because the T400 would not take it. I ended up buying a stick of RAM off fleabay with my fingers crossed and was relieved when the T400 booted up to OS without the beeping.

[RealBlackStuff]

RAM modules corrode after a while.
Use an eraser on the gold contacts on both sides of the module, until they shine. Don't touch!
Remove any eraser-remnants with either a brush or blow them off.
Then try again.
Maybe the RAM slot contacts are corroded as well. Inserting/removing a module a few times might help.
Other than that, I can't think of a good reason for them not to work.

[schen]

Thanks guys. I didn't think that there was any good reason or known issue related to the order or the RAM slots. I guess it was just one of those things and I'll chalk it up to experience! At least I've got one 2Gb module in there and it's running with the 3Gb max.

[TuuS]

mismatched ram modules will behave this way sometimes, different speeds, different size, or even different manufactures can sometimes not play nice together. There could be many reasons such as oxidation/residue on the contacts. RBS gave very good advice, but make sure the eraser is clean before you begin and I usually clean with a Qtip and alcohol too, just make sure it's dry before you install.

I would also run a memory test on the modules, even if it works with the 2gb on top, only the vital areas of memory are tested at boot by default (to decrease boot time), so make sure you don't have a bad module. Sometimes a bad sector will work and not be noticed until the computer tries to use it in which case you could get BSOD crash or other errors.